This is done by changing the CD-Key license to be volume/corporate, which doesn't require a CD-Key. The CD-Key license can only be changed like this if having the MSDN CD.

To change the CD-Key license of you Windows 2000, edit the install file X:\i386\setupp.ini :

Pid=51873XXX

Usually the "XXX" is three zeros "000", replace them with "270" (Corporate) so it looks like this :

Pid=51873270

Credits TheTechGuide.com